IFCONFIG(8C) IFCONFIG(8C) NAME ifconfig - configure network interface parameters SYOPNSIS /etc/ifconfig interface address_family [ _a_d_d_r_e_s_s [ _d_e_s_t__a_d_d_r_e_s_s ] ] [ _p_a_r_a_m_e_t_e_r_s ] /etc/ifconfig interface [ protocol_family ] DESCRIPTION _I_f_c_o_n_f_i_g is used to assign an address to a network interface and/or configure network interface parameters. _I_f_c_o_n_f_i_g must be used at boot time to define the network address of each interface present on a machine; it may also be used at a later time to redefine an interface’s address or other operating parameters. The _i_n_t_e_r_f_a_c_e parameter is a string of the form ‘‘name unit’’, e.g. ‘‘en0’’. Since an interface may receive transmissions in differing protocols, each of which may require separate naming schemes, it is necessary to specify the _a_d_d_r_e_s_s__f_a_m_i_l_y, which may change the interpretation of the remaining parameters. The address families currently supported are ‘‘inet’’ and ‘‘ns’’. For the DARPA-Internet family, the address is either a host name present in the host name data base, _h_o_s_t_s(5), or a DARPA Internet address expressed in the Internet standard ‘‘dot notation’’. For the Xerox Network Systems(tm) family, addresses are _n_e_t_:_a_._b_._c_._d_._e_._f, where _n_e_t is the assigned network number (in decimal), and each of the six bytes of the host number, _a through _f, are specified in hexadecimal. The host number may be omitted on 10Mb/s Ethernet interfaces, which use the hardware physical address, and on interfaces other than the first. The following parameters may be set with _i_f_c_o_n_f_i_g: up Mark an interface ‘‘up’’. This may be used to enable an interface after an ‘‘ifconfig down.’’ It happens auto‐ matically when setting the first address on an inter‐ face. If the interface was reset when previously marked down, the hardware will be re-initialized. down Mark an interface ‘‘down’’. When an interface is marked ‘‘down’’, the system will not attempt to transmit mes‐ sages through that interface. If possible, the inter‐ face will be reset to disable reception as well. This action does not automatically disable routes using the interface. trailers Request the use of a ‘‘trailer’’ link level encapsula‐ tion when sending (default). If a network interface supports _t_r_a_i_l_e_r_s, the system will, when possible, encapsulate outgoing messages in a manner which mini‐ mizes the number of memory to memory copy operations performed by the receiver. On networks that support the Address Resolution Protocol (see _a_r_p(4P); currently, only 10 Mb/s Ethernet), this flag indicates that the system should request that other systems use trailers when sending to this host. Similarly, trailer encapsu‐ lations will be sent to other hosts that have made such requests. Currently used by Internet protocols only. -trailers Disable the use of a ‘‘trailer’’ link level encapsula‐ tion. arp Enable the use of the Address Resolution Protocol in mapping between network level addresses and link level addresses (default). This is currently implemented for mapping between DARPA Internet addresses and 10Mb/s Eth‐ ernet addresses. -arp Disable the use of the Address Resolution Protocol. metric _n Set the routing metric of the interface to _n, default 0. The routing metric is used by the routing protocol (_r_o_u_t_e_d(8c)). Higher metrics have the effect of making a route less favorable; metrics are counted as addition hops to the destination network or host. debug Enable driver dependent debugging code; usually, this turns on extra console error logging. -debug Disable driver dependent debugging code. netmask _m_a_s_k (Inet only) Specify how much of the address to reserve for subdividing networks into sub-networks. The mask includes the network part of the local address and the subnet part, which is taken from the host field of the address. The mask can be specified as a single hexadec‐ imal number with a leading 0x, with a dot-notation Internet address, or with a pseudo-network name listed in the network table _n_e_t_w_o_r_k_s(5). The mask contains 1’s for the bit positions in the 32-bit address which are to be used for the network and subnet parts, and 0’s for the host part. The mask should contain at least the standard network portion, and the subnet field should be contiguous with the network portion. dstaddr Specify the address of the correspondent on the other end of a point to point link. broadcast (Inet only) Specify the address to use to represent broadcasts to the network. The default broadcast address is the address with a host part of all 1’s. ipdst (NS only) This is used to specify an Internet host who is willing to receive ip packets encapsulating NS pack‐ ets bound for a remote network. In this case, an appar‐ ent point to point link is constructed, and the address specified will be taken as the NS address and network of the destinee. _I_f_c_o_n_f_i_g displays the current configuration for a network interface when no optional parameters are supplied. If a protocol family is specified, Ifconfig will report only the details specific to that pro‐ tocol family. Only the super-user may modify the configuration of a network inter‐ face. DIAGNOSTICS Messages indicating the specified interface does not exit, the requested address is unknown, or the user is not privileged and tried to alter an interface’s configuration. SEE ALSO netstat(1), intro(4N), rc(8) 4.2 Berkeley Distribution May 22, 1986 IFCONFIG(8C)